The subject matter disclosed herein relates generally to imaging systems, and more particularly to methods and systems for generating a Positron Emission Tomography (PET) attenuation correction map.
Multi-modality imaging systems exist that scan using different modalities, for example, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), and Single Photon Emission Computed Tomography (SPECT). For example, one known multi-modality imaging system includes a PET imaging system and a CT imaging system. In operation, PET and CT information is acquired from the PET and CT and imaging systems, respectively. The acquired PET and CT information is then processed to reconstruct a set of PET images, a set of CT images, and/or a set of fused PET/CT images.
In a PET/CT system, the PET images are typically reconstructed using attenuation correction. For example, information generated by the CT system may be utilized to generate a set of attenuation correction factors that may be applied, to the PET images. In general, the attenuation correction factors correlate to a density of the object being imaged. Accordingly a plurality of attenuation correction factors may, for example, be derived from CT density information that is generated during a CT scan, wherein the CT system is specifically configured to generate density information that may be utilized to generate the attenuation correction factors. Thus, in a PET/CT imaging system, the density information may be acquired directly from the CT information to generate an attenuation correction map which may then be applied to attenuation correct the PET data.
Multi-modality imaging systems may also be configured as a PET/MR imaging system. However, if the multi-modality imaging system is configured as a PET/MR system, the MR information cannot be directly used to estimate the attenuation correction factors to reconstruct a PET image. More specifically, the information in an MR image is generally not directly related to density. Therefore, the MR information cannot be used directly to generate an attenuation correction map for attenuation correcting PET data.